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Doug McArthur

The Icom IC 910-H VHF/UHF Transceiver, because of its single master oscillator, lends itself exceedingly well to lock this Radio to a Rubidium Standard and thus achieve precise frequency stability and frequency readout.

Tim Tuck VK2XTT has produced an excellent paper on this project and initially attracted my attention to a relatively simple approach to achieve my aim. I am indebted to his help and advice during construction of the Project. please refer to his paper here.

I have made some minor changes to Tim's design mainly to reflect the different Rubidium Oscillator configuration. I have used a different amplifier to provide additional level to drive two IC-910H transceivers. This and other and useful information regarding the project I have compiled and included in this link. click here.

For commented photos of the project please click here.

Bob Campbell VK4XV has done extensive investigation into the 'non programable' version and essential supplementary information is available here. Bob has also developed a program to adjust the 10MHz output reference frequency. You may down load that software [zip] here. Note this software is different to the 'prograble version'.

*** DON'T APPLY +5v to DB connector pin 3 .. READ BOB's VK4XV PAPER ABOVE even though the supplier may label that connection as requiring +5v ***

I have also added photos of the inside of a FE-5680A as well the inner workings of the Rubidium Cell. Iin the same gallery I have included photos of a dual Rubidium Standard project that I use for locking my test equipment. This is fully portable, provides a 10MHz reference as well as a programable source, and does not require an outside antennae like a convential GPS. There are also pictures of my HB GPS 10MHz reference as well.

In the above photos I have included close ups of the Rubidium physics package and the Rb lamp. There has been a comment regarding the reliability of the Rb Lamp and it was suggested that units, when purchased from EBay sources, may be at the end of their useful life expectancy . These units have, in the main, been removed old Motorola CDMA base Stations and it is conceded that some could be approaching its end of their useful life. Not withstanding such comments, I have 4 of these units and all reach lock in less than 3 minutes, which I am told, is a very good indication that they are very much in the 'prime' of their life! Moreover I have opened one up (as has Tim VK2XXT) and we both have found no signs of splattering on the Rb Glass bulb which also is a good indication that the Rb bulb is in good condition. It is not to say that premature component failure, due to the high temperature surrounding the cell will not occur, but for mine, my lamp will most likely go out before my Rb cell!!

However... if the Rb cell does shows signs of failure (long lock up times or just stops) all is not lost. Gerald Molenkamp VK3GJM has been rejuvenating Rb cells successfully for a considerable time and has agreed to provide his paper on the method as a reference. The globe in question is from a EFRATOM Model FRS-C 10MHz Rubidium Clock, which is very similar to those found in the FE-5680A series. We believe the same principal of rejunenating can be applied in this case. Gerald's excellent article may be down loaded here.

Matthius Bopp DD1US has also done considerable work on developing a precise frequency standard using the FE 5680A and his paper (mentioned also in the VK2XTT reference) can be down loaded here as well.

I have also included a Technical Manual for the FE 5680A series and that can be down loaded here.

A word of advice before purchasing a FE 5680A .. They are not all the same and care must be taken to buy one that can be programmed. (refer my supplementary information above)